<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>首页</title>
</head>
<body>
<div style="width: 100px;height: 100px;background-color: lime">
<div style="width: 50px;height: 50px;background-color: red"></div>
</div>
</body>
</html>